Computer users often access information, computer files, or other resources of computer networks from locations that are geographically or logically separate from the networks. This is referred to as remote access. For example, a user of a host or client that is part of a local area network (“LAN”) may want to retrieve information that resides on a computer that is part of a remote network. Before a user can gain access to that computer, the user must first obtain permission to do so. In the interest of data integrity, and data confidentiality, many computer networks have implemented integrity and access control mechanisms to guard against unwanted network traffic or access by unauthorized users. On the other hand, a corporation may institute policies that restrict its employees from accessing certain web sites on the internet while using the corporation's computer resources. For example, Corporation C may disallow access to pornographic web sites. Corporation C's access control mechanism would prevent the employees from accessing such sites.
An example of an access control mechanism is a server that implements authentication, authorization, and accounting (“AAA”) functions. Authentication is the process of verifying that the user who is attempting to gain access is authorized to access the network and is who he says he is. Generally, after authentication of a user, an authorization phase is carried out. Authorization is the process of defining what resources of the network an authenticated user can access.
Several authentication and authorization mechanisms are suitable for use with operating systems that are used by network devices, such as the Internetworking Operating System (“IOS”) commercially available from Cisco Systems, Inc. However, most prior authentication and authorization mechanisms are associated with dial-up interfaces, which can create network security problems. In a dial-up configuration, a remote client uses a telephone line and modem to dial up a compatible modem that is coupled to a server of the network that the remote client wishes to access. In another dial-up Configuration, a remote client first establishes a dial-up connection to a server associated with an Internet Service Provider, and that server then connects to the network server through the global, public, packet-switched internetwork known as the Internet. In this configuration, the network server is coupled directly or indirectly to the Internet.
Unfortunately, information requests and other traffic directed at a network server from the Internet is normally considered risky, untrusted traffic. An organization that owns or operates a network server can protect itself from unauthorized users or from unwanted traffic from the Internet by using a firewall. A firewall may comprise a router that executes a “packet filter” computer program. The packet filter can selectively prevent information packets from passing through the router, on a path from one network to another. The packet filter can be configured to specify which packets are permitted to pass through the router and which should be blocked. By placing a firewall on each external network connection, an organization can prevent unauthorized users from interfering with the organization's network of computers. Similarly, the firewall can be configured to prevent the users of the organization's network of computers from accessing certain undesirable web sites on the Internet.
One common method of remote access using the Internet is telnet, a protocol used to support remote login sessions that defines how local and remote computers talk to each other to support a remote login session “Telnet” is also the name of a remote login program commonly used in networks based on Transmission Control Protocol/Internet Protocol (“TCP/IP”), a set of protocols that define how communications occur over the Internet. Past authentication and authorization mechanisms were produced to work with firewalls in the context of telnet. An example of an authentication and authorization mechanism that works with telnet is “Lock and Key” for IOS, commercially available from Cisco Systems, Inc.
However, a major drawback of telnet is that the client must know, before making any connection request, the Internet Protocol address (“IP address”) of the firewall that is protecting the target network which the client is attempting to access. An IP address is a unique 32-bit binary number assigned to each firewall, router, host computer or other network element that communicates using IP. Obtaining the IP address of a firewall can be inconvenient or impractical because there are so many IP addresses currently assigned to network devices. Further, IP addresses normally are guarded closely by the network owner, because knowledge of an IP address enables unauthorized traffic to reach the device identified by the IP address.
Moreover, once a user successfully uses the authentication and authorization mechanism to secure a logical path through the firewall, the user may be restricted to one type of network traffic for the connection. For example, a firewall can be configured to provide a path through the firewall for a specific type of network traffic as specified by a user profile that is associated with each authenticated user. The user profile contains information on what the user is authorized to do on the network. The user profile may specify, for example, that the user may use only File Transfer Protocol (“FTP”) traffic. Thus, the user may use the path through the firewall only for FTP traffic, for the duration of that connection. Furthermore, the user profile associated with the user contains a specific IP address that specifies the host or client from which the user can attempt to secure a logical path through the firewall. Thus, a user is not free to use any one of several computers that may be available to access the target network. Also, the user may not be free to use a client in a network that employs Dynamic Host Configuration Protocol (DHCP). DHCP assigns dynamic IP addresses to the devices on a network. Thus, a client in a DHCP environment can have a different IP address every time it connects to the network.
Based on the foregoing, there is a clear need for a mechanism allowing users to use remote access via the Internet without requiring advance knowledge of the IP address of the firewall router, and without restricting a user to a particular host or client.
In particular, there is a need for an authentication and authorization mechanism in the context of remote access via the Internet that does not rely on telnet and that allows the passage of different types of traffic for a given connection.